| Abstrakt: |
During mineralogical investigations of breccia and volcanic rocks of the Terny structure (Veseli Terny, Kryvyi Rih), so-called Terny meteoritic crater, the mineral tourmaline, previously unknown here, was found. Tourmaline crystals, with a length from 0.05 to 1.0 mm and more and up to 0.1—0.2 mm wide, are associated with quartz, potassium feldspar, graphite and apatite. The morphology and chemical composition of tourmaline were examined using optical microscope and EРМA in transparent thin sections. The tourmaline crystals are unusually parted along two transverse systems of microcracks oriented obliquely to the prism faces. EPMA reveals that tourmaline is dravite. The specific deformations of dravite and observed mineral associations probably indicate the rock formation under conditions of high pressures and temperatures of impact metamorphism. It is also confirmed by the presence of planar fractures in quartz. [ABSTRACT FROM AUTHOR] |
